1. Field of the Invention
This invention relates to a shielding terminal for a coaxial cable, and more particularly to an improved coaxial cable shielding terminal which has a press-clamping portion for press-connection to an end portion of the coaxial cable, and is electrically connected to a braid of the coaxial cable exposed at the end portion thereof.
2. Related Art
Generally, in order to intercept electrical noises such as electromagnetic waves and static electricity, a coaxial cable, used as an antenna wire or the like, has a construction in which a conductor core is covered with an inner insulating layer, and this inner insulating layer is covered with a braid, and further this braid is covered with an insulating sheath.
There have been proposed various coaxial connectors for connecting such a coaxial cable to a mating equipment or a mating connector.
A coaxial cable shielding terminal for connecting the braid of the coaxial cable to the mating connector for grounding purposes is used in such a coaxial connector, and one example thereof is shown in FIGS. 6 and 7 (see, for example, JP-UM-A-5-90855).
The conventional coaxial cable shielding terminal 11, shown in FIG. 6, is a press-shaped product formed of a metal sheet, and a connector mounting portion 13 is provided at a distal end portion thereof, while a press-clamping portion 14 for press-connection to the coaxial cable 1 is provided at a proximal end portion thereof.
In the coaxial cable 1, an insulating sheath 3 and a braid 5, provided inside this insulating sheath, are cut off over a predetermined length to expose two core wires 7, and then a distal end portion of an inner insulating layer 7b of each core wire 7 is cut off to expose a conductor core 7a, and then a wire press-clamping terminal (not shown) is press-clamped to a distal end portion of the conductor core 7a, and these terminals are mounted on a connector 15.
The connector mounting portion 13 includes a pair of side walls 13a and 13a extending upright respectively from opposite side edges of a terminal bottom plate portion 11a at a distal end portion thereof, and a connector housing 15 (to which the core wires 7 are connected) is held between these side walls 13a and 13a, and this connector mounting portion 13 is covered with a cover 25 as shown in FIG. 7.
The press-clamping portion 14 has a connection piece 12 provided between a pair of press-fastening portions 14a and 14b, and this connection piece 12 is inserted between the braid 5 of the coaxial cable 1 and the inner insulating layer 7b disposed inside this braid.
An interconnecting portion 12a is formed on an upper edge of one side wall 13a, and is spaced a predetermined distance forwardly from the press-fastening portion 14a, and is bent toward the terminal bottom plate portion 11a, and the connection piece 12 is folded back toward the rear end in generally parallel, spaced relation to the press-fastening portion 14a through the interconnecting portion 12a, and is curved into an arcuate cross-section so as to be disposed along the outer peripheral surface of the core wire 7.
For connecting the coaxial cable shielding terminal 11 to the coaxial cable 1, the connection piece 12 is inserted between the braid 5 and the inner insulating layer 7b, and in this condition the pair of press-fastening portions 14a and 14b are press-fastened on the insulating sheath 3.
As a result, the press-fastening portion 14a presses and urges the insulating sheath 3 and the braid 5 toward the connection piece 12, so that the connection piece 12 is held in intimate contact with the inner peripheral surface of the braid 5 as shown in FIG. 8, and therefore a good electrically-connected condition is obtained between the braid 5 and the coaxial cable shielding terminal 11 via the connection piece 12.
In the above coaxial cable shielding terminal 11, however, when the press-fastening portion 14a of the press-clamping portion 14 was press-fastened, the connection piece 12 was displaced toward the conductor core 7a (as indicated by arrow A in FIG. 8) by the pressing force applied during this press-fastening operation. The deformed connection piece 12 bit into the inner insulating layer 7b, so that the braid 5 could not be sufficiently compressed, and in some cases, a good electrically-connected condition could not be obtained.
And besides, when the thus deformed connection piece 12 squeezed the inner insulating layer 7b around the conductor core 7a, the distance between the conductor core 7a and the braid 5 was changed (that is, the ratio (d1/d2) of the diameter d1 of the conductor core 7a to the outer diameter d2 of the inner insulating layer 7b therearound was changed), and this invited a problem that an impedance in the coaxial cable 1 was disturbed, thereby adversely affecting high-frequency characteristics.